With the aim of understanding the synaptic organization of neurons in the vertebrate retina intracellular recordings of their responses to light stimuli of varying spatial and chromatic composition are made. The responses of all of the neuronal types in the retina, including receptors, have been shown to be modified by changes in the pattern of wavenlength of light falling on the retina indicating that these cells receive synaptic input from spatially separate protions of the retina. By examining in detail the nature of these changes it should be possible to determine the pathways underlying these synaptic interactions in the various cell types. In addition, cells recorded from are stained with a fluorescent dye developed by Mr. Walter Stewart of LEP/NIAMDD which is passed into the cell iontophoretically from the recording electrode. This technique provides a basic for correlating the physiological properties of the cell with its structure. This new dye appears far superior to the previously used intracellular stain, Procion yellow, in both its quantum yield and ability to diffuse throughout the cell, thus providing a means of making more precise anatomical -physiological correlations.